When photocopiers were first used, charging of the photoreceptor or photoconductive plate was usually accomplished by rubbing the photoconductive surface with electronic charging materials, such as rabbit fur. Today much more sophisticated charging means are used; in particular, corona charges. Generally, the corona charger comprises an array of charge emitting pins located in close proximity to a corona grid. The pins emit the charge and convey this charge to a conductive grid, which provides uniformity of charge across the entire used surface of the photoreceptor. The grid is specifically configured so as to have uniform charge emitting capabilities across its entire longitudinal surface. It is especially important to maintain the grid surface in condition where it will provide this uniform charge distribution across the photoreceptor or photoconductive surface. Once a uniform charge is placed by the grid across the photoreceptor surface, the remainder of the imaging process is followed, i.e., exposure of image, dissipation of charge in image configuration, contact with toner and fixing of toner image on a paper or receptive surface.
Contamination of the inner and outer sides of the grid could lead to print quality defects such as streaks, image quality and other performance problems. Examples of image quality failures would be half tone non-uniformities and white and dark streaks in the final image. Also, the life of the corona charging mechanism can be adversely affected if the grid is not kept uniformly clear of contaminants, such as toner.
There are used today various corona cleaning methods and apparatus to remove the toner build up and other contaminates from the grid. Traditionally, these corona cleaning devices have focused on cleaning the pins, wires and inside or inner surface of the corona grid. However, cleaning the grid surface closest to the photoreceptor (outer surface) grid has been neglected. This could be due to concerns about scratching or contacting the photoreceptor surface during any grid cleaning operation. As a result, the corona grid (photoreceptor side) or outside grid surface has not been effectively cleaned of toner build up or other contaminants. Due to this lack of cleaning of the photoreceptor side (outer side) of the grid, a number of image quality problems may result. Also, as noted above, the useful life of the corona device could be shortened if proper grid cleaning is not observed. Typical spacing between the grid and photoreceptor is 1-2 mm, leaving insufficient room for a cleaning device to sweep across the outside grid surface.